Modeling of induced currents from electrodynamic tethers in a laboratory plasma

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Abstract
The presently accepted picture of the current path for electrodynamic tethers envisions a quasi‐dc current flow in a “phantom loop” consisting of the tether, two field‐aligned current channels into the ionosphere and a cross‐field dosing current in the E‐layer. Predictions are made on the establishment and maintenance of a current loop in space based on observations of time‐dependent currents between tethered electrodes in a large laboratory magnetoplasma, In addition to radiation from the contactors (“whistler wings”), the insulated tether is observed to emit waves (a “whistler wedge”). The “wedge” provides closure during loop formation by carrying cross‐field polarization currents. Whistler spread within the ray cone leads to overlapping of the current wings not far from the tether hence minimizing the role of the ionospheric closure. Maintenance of the loop requires the continuous emission of whistler waves by the entire tether thereby providing severe radiation losses.